Why is My HVAC Making That Noise?

When your air conditioning is working perfectly, a low hum might be the only sound you hear coming out of your HVAC unit... and you might not even 'hear' it since it's likely a common background noise for you in Pennsylvania's summer heat.

On the other hand, if you're being startled by strange noises you're not used to hearing, it's important to have these sounds looked into. What is "just a little annoying" today may be very costly to fix if you don't get them checked out right away. We're going to walk you through five 'weird sounds' your HVAC might be making... and what to do about them.

Rattling, Clanking, or Banging

Odds are good that these sounds are coming from an issue with the blower assembly or motor. A persistent rattle is coming from a component within the system that has come loose, and should be repaired immediately before the part breaks or disconnects entirely. Louder 'banging' sounds, if they are most noticeable when the blower is running, need immediate attention. If you hear a loud banging sound, please shut your system off immediately and give us a call. Something has broken or been completely disconnected and your system needs immediate repair.

A 'rattling' sound may also come from motor bearings. When you sign up for preventative maintenance on your HVAC with our Gold Star program, you'll be able to rest assured that your motor assembly will be checked over as part of our twice-annual visit in order to prevent this problem from occuring.

Repetitive Clicking

Note: We're not thinking of the occasional single click when the HVAC unit turns on or off. That's perfectly normal, and just a sign that your system has kicked on or turned off like it's supposed to. However, if this 'clicking' noise is repeated and it is coming from either the control panel or outside compressor, you may be looking at a defective relay. Electrical control issues could also cause the relay to timeout and fail.

The solution to this issue may be an easy, quick repair, but it's important to schedule a visit as soon as you realize the clicking is happening in order for us to help you with the repair before your system breaks down.

A Sound You Can Only Describe as a "Thwap"

If your blower is running and you hear a sound that is best described as 'thwapping', you may be dealing with some sort of debris stuck in the blower blades or possibly something inside the housing that is knocking into the blower while it turns. If you're wondering what 'thwap' refers to, try to think of the way that playing cards sound when attached to a bicycle's tire. This noise is not usually indicative of a critical problem, but the resistance created by the constant contact with whatever debris is in the way will cause your motor to wear down faster over time, leading to the eventual need for replacement before it otherwise would be.

Squealing or Screeching Noises

Just like in a car, a 'squeal' or 'screech' from your HVAC can indicate that your unit's belt is going bad. These are not normally expensive to repair, but it is important to replace them before they break and your blower quits working as well.

A screeching noise, on the other hand, could be a blower issue that can be solved with a little bit of oil. Many blower units have an area for adding in lubricant, while others are sealed. If you're able to add oil in on your own, be sure to use the correct oil. The WD-40 or basic 3-in-1 oil that many households have in hand simply isn't going to work for this particular application. Give us a call and we can walk you through what oil would be the right choice for you.

Finally... Rattling From Outside the Compressor/Fan Unit

You should never hear a rattle when the fan turns on inside your compressor unit. Loose hardware or a failing motor may be the cause, and both of these issues need to be dealt with right away. The louder the sound gets, the more serious the problem is likely to be. If the rattling sound begins to be accompanied by or is replaced by what sounds like a scream, schedule a visit from a professional right away. Your compressor may be failing and needs immediate attention.

Need Help Diagnosing a Noise? Give Us a Call Today!

At Donnelly's Plumbing Heating and Cooling, we've heard just about every 'weird noise' an HVAC unit is capable of making, and our experienced technicians are happy to come out and take a look (or a listen) to help you figure out what exactly is going wrong with your HVAC and how to fix it. We've had over forty years in the business of providing exceptional heating, cooling, and plumbing services here in Eastern Pennsylvania, and it's our mission to keep your home comfortable all year long. Reach us by phone at (215) 855-2014 or contact us online at any time to schedule service today!